Following are the elements usually found in steel and the general influence they have upon the physical properties. In each case' the statements are my own opinions. In a general way they will be agreed to by almost all metallurgists, as far as structural steel is concerned.
Silicon: This element is seldom present in structural steel in quantities greater than a trace, and tlie effect of these minute quantities may be ignored. It is present in steel castings in amounts up to four-tenths of one per cent., but its influence is not great for better or for worse.
Copper: This element has some influence on the hot properties, but not as much as. generally supposed, as its effect is often masked by sulphur, with which it is generally associated. It has no effect, on the cold properties as far as known.
Manganese: The most important function of this element is to give ductility while the steel is hot, so that the piece can be rolled into finished form without tearing. Ordinary structural steels contain from .30 to .GO per cent, and within these limits it has very little influence upon either^ the tensile strength or the ductility. Above this amount it adds to the tensile strength, but does not materially decrease the 'ductility. It would seem, however, to slightly increase its liability to break under shock, although this is not proven. •
Sulphur: This element has just the opposite effect from manganese and makes the steel crack while it is being hot rolled. After the metal is cold it seems to have no appreciable effect upon the physical properties.
Phosphorus: This'element has little effect upon the hot properties, but in the cold state it makes'the steel brittle and adds to the tensile strength in about the same degree as carbon. In ether words an increase of one-hundredth of one per cent. (.01 per cent.) of phosphorus increases the tensile strength about one thousand pounds per square inch. In ordinary steels the phosphorus is always limited to one-tenth of one per cent. In special steela much lower limits are given. :
Carl)on: This is the one element used above all others by manufacturers in getting required physical properties. An increase of one-hundredth of one per cent. (.01 per cent.) gives an increase in tensile strength of about 1000 pounds per square inch. It decreases the ductility slightly and regularly. When steel is heated